The Amman Valley’s most notorious eyesore is to undergo the final steps of its transformation following the agreement of a deal between the local authority and an un-named property developer.

County Hall officials remain tight-lipped as to the identity of the developer – and the specific plans for Arcade Terrace in Garnant, but the Guardian can exclusively reveal that the redeveloped site will see the construction of a supermarket with residential flats above.

The Guardian also understands that the development company already has an agreement in place with convenience retailer One-Stop, an off-shoot of the supermarket giant Tesco, to take over the retail unit once construction is complete.

Arcade Terrace on Cwmamman Road spent 30 years as a rat-infested derelict row until the majority of the row – which was built during the First World War by local shopkeeper Morgan Jeffreys – was torn down by Carmarthenshire County Council in 2012.

The current deal involves the vacant land and the long-empty Shades hair studio next door.

The deal will be seen as a triumph for Garnant county councillor Kevin Madge, who has spent more than three decades battling to see the site redeveloped and was overjoyed at the news.

“This will be a major investment in the Amman Valley and I am absolutely delighted to hear the news,” said Cllr Madge.

“Arcade Terrace has been this valley’s biggest eyesore for many, many years and the redevelopment of the site has been a long time coming.

“The possibility of affordable housing in the village is to be greatly welcomed and it seems fitting that there will be a shop on the site, just as it was when Arcade Terrace first opened and over many generations up into the 1980s.

“I am delighted that after all these years Arcade Terrace might at least be returning to its former self.”

Carmarthenshire County Council’s Head of Corporate Property Jonathan Fearn said: “The site was subject to a tendering process and the preferred bidder has been selected.

“Solicitors have been instructed and the sale is now going through the legal process.”